Nitrification Alkalinity Consumption Rate Calculator
Calculate Alkalinity Drawdown
Determines the stoichiometric destruction of alkalinity during biofiltration, applying the constant 7.14 grams of CaCO3 consumed per gram of TAN fully oxidized to nitrate.
Understand Nitrification Alkalinity Consumption in RAS
For RAS facility designers and process engineers sizing chemical dosing infrastructure, this tool quantifies the daily alkalinity drawdown caused by nitrification so you can accurately dimension lime or soda ash feed pumps and prevent pH crashes that inhibit biofilter performance. Accurate alkalinity management is critical for maintaining stable pH, which directly impacts the efficiency of nitrification and overall system health. Preventing pH crashes is essential, as low pH can quickly stress aquatic life and halt beneficial bacterial activity.
This calculator is a preliminary estimation tool only and is not a substitute for review by a qualified and licensed engineer. Always consider site-specific factors and consult with experts for final design and operational decisions.
How to Use This Calculator
- Enter the predicted daily TAN load entering the biofilter in kilograms.
- Read the calculated alkalinity consumption displayed in kg/day of CaCO3 equivalent.
- Subtract this value from your incoming alkalinity reserve to determine the net dose required for your pH control system.
FAQ
Q: How much alkalinity does nitrification consume per unit of ammonia?
A: Full oxidation of TAN to nitrate consumes exactly 7.14 grams of CaCO3 alkalinity for every gram of TAN oxidized, derived from the stoichiometric reaction NH4+ + 2O2 → NO3- + H+ + H2O.
Q: Is the 7.14 coefficient always accurate for my RAS?
A: The 7.14 g/g factor represents theoretical maximum consumption assuming all energy supports maintenance. Biological synthesis of biomass typically reduces actual consumption to approximately 6.0–6.5 g/g, but engineering standards use 7.14 as a conservative baseline to guarantee sufficient alkalinity reserves.
Q: Does this calculator apply to nitritation (partial nitrification)?
A: No. This tool calculates consumption for complete oxidation to nitrate. Partial nitrification stopping at nitrite consumes only ~3.57 g CaCO3 per g TAN; use this calculator only when your biofilter design targets full nitrate production.
Q: My alkalinity is falling faster than this calculation predicts—what should I check?
A: Verify TAN sensor calibration and account for other acid sources like CO2 off-gassing or organic decay. If TAN is stable but alkalinity drops rapidly, suspect sulfate reduction or septic zones; correlate your ammonia profile using our Unionized Ammonia Toxicity Fraction Calculator to rule out toxicity masking.